1. Field of the Invention
The present invention relates to a device to facilitate the tying of surgical sutures at remote sites within the body during endoscopic surgery and other minimally invasive surgical procedures. A method for tying surgical knots in a suture at intracorporeal positions during minimally invasive surgery is also presented.
2. Background Art
Minimally invasive surgical techniques have emerged as an important trend within the field of surgery. Minimally invasive surgery differs from standard open surgery in that surgical procedures are performed through small incisions in the body under the guidance of endoscopy, fluoroscopy, ultrasound or other remote imaging techniques. Minimally invasive surgical techniques reduce the morbidity of surgical procedures, accelerate patient recovery and, in many cases, also reduce the overall cost of surgery, especially by shortening the recovery period during which patients must stay in the hospital.
Due to such benefits, many established surgical procedures, such as arthoscopic knee surgery and gall bladder removal, have been converted from open surgical techniques to minimally invasive surgical techniques. Minimally invasive surgery includes laparoscopic, endoscopic and orthoscopic surgeries. In performing laparoscopic surgery, for example, procedures are performed in the abdominal cavity by making a small incision through several layers of tissue, which may include the outer layer of skin called the epidermis, a layer of fat beneath the epidermis, a layer of abdominal muscle tissue beneath the fat layer and the lining of the abdominal cavity called the peritoneum. A trocar is inserted through the incision and medical instruments are introduced into the abdominal cavity therethrough. The surgeon performs procedures inside the cavity by manipulating the medical instruments from outside the patient while viewing the manipulations using a closed circuit monitor connected to an imaging device called a laparoscope that is inserted into the cavity. By using such equipment and procedures, laparoscopic surgery generally results in less trauma to the patient and, consequently, a more rapid recovery than with conventional open surgery. Similar advantages apply to other forms of minimally invasive surgery.
One of the great challenges facing minimally invasive surgery is the advancement of minimally invasive surgical techniques into the area of cardiac surgery. Certain cardiac surgery procedures that previously were only possible through open chest surgery have already been converted to minimally invasive surgical techniques. For example, catheter techniques have been developed for occlusion of patent material septal defects and for valvuloplasty of stenotic aortic or mitral valves. Instruments and techniques have also been developed for endoscopic approaches to the heart, allowing more complex cardiac surgical procedures, for example, the replacement of a stenotic or insufficient mitral valve, to be performed through minimally invasive surgical techniques.
One of the important challenges in minimally invasive surgical techniques is that of placing sutures in the tissue at the operating site and applying properly tied suture knots through the narrow access of an endoscopic cannula or other equally restrictive access passage. Two different approaches are commonly used in tying sutures in endoscopic surgery. These can be classified generally as intracorporeal knot tying techniques, for tying sutures at the surgical site within the body, and extracorporeal knot tying techniques, which allow knots to be tied in the sutures outside of the body, then transferred to the surgical site using a knot pusher.
Intracorporeal knot tying can be performed using endoscopic graspers or forceps to manipulate the sutures in a technique similar to instrumented knot tying in conventional surgery. Alternatively, specialized intracorporeal knot tiers can be used.
Various intracorporeal knot tiers are shown in U.S. Pat. No. 5,234,443 to Phan et al., U.S. Pat. No. 4,641,652 to Hutterer et al. and U.S. Pat. No. 5,281,236 to Bagnato et al. Tying sutures using a grasper or an intracorporeal knot tier is difficult and tedious compared with standard bimanual methods of surgical knot tying. Using intracorporeal knot tiers usually requires specialized training in operating the instrument and, even in the hands of the most skilled operators, usually requires more time than standard knot tying techniques. In procedures where few knots have to be tied, where access to the surgical site is difficult, or where the length of the procedure is not critical, intracorporeal knot is the likely method of choice.
However, for the surgical replacement of a diseased mitral valve using closed chest surgical procedures, the complexity and time consumption of using intracorporeal knot tying techniques can endanger the patient since the rate of post-surgical complications in cardiac procedures rises in proportion to the length of time that the patient must spend on cardiopulmonary bypass. The time spent using intracorporeal knot techniques in a surgical procedure, such as mitral valve replacement, that can involve tying a multitude of individual multiple-throw suture knots, with up to four (4) or more throws per suture, unnecessarily endangers the patient. Due to the proportional increase in patient risk, it is important to keep the duration of the procedure as short as possible and avoid any unnecessary delays.
Therefore, in time sensitive procedures, it is best to take advantage of an experienced surgeon's practiced and well honed bimanual surgical knot tying skill, rather than to require the surgeon to use complex intracorporeal knot tying techniques. Some knot pushers are designed specifically to take advantage of this prior skill by allowing the surgeon to form the suture knots extracorporeally, then using the knot pusher to transfer the knots to the surgical site and tighten them in place. A well designed knot pusher allows the surgeon to use a knot tying technique that closely mimics the standard bimanual knot tying technique and does not add undue complication to the procedure.
A common type of surgical knot pusher is made with a C-shaped loop on the distal end of an elongated shaft, as exemplified in U.S. Pat. No. 3,871,379 to Clarke. The opening of the C faces distally from the shaft, and the opening is sized to pass the desired size of suture. These devices are used by first passing the suture through the tissue to be tied and bringing both ends of the suture out through the surgical entry point so that a knot can be tied extracorporeally. The C-shaped loop is then placed over the knot and is used to slide the knot down the suture to the surgical site. The knot may then be tightened by pulling on the suture ends. This type of knot pusher has several disadvantages. The knot pusher must be reloaded onto the suture thread each time another throw is added to the suture knot. This adds time and complexity to the tying technique. In many cases, the orientation of the C-shaped loop on the knot pusher prevents the knot from being pushed directly up to the tissue that is to be sutured. This can leave a bit of slack in the suture that would be a severe problem in valve replacement surgery because it could cause the replacement valve to loosen and potentially displace from its proper position in the heart or could lead to perivalvar leaks. The open gap of the C-shaped loop can accidentally drop the suture while pushing the knot down if it is not carefully handled. This can be very frustrating to the surgeon because the knot pusher will have to be rethreaded, which is much more difficult once the knot is halfway down the suture and within the body cavity. Also, the knot pusher has no means to insure that the knot remains centered on the knot pusher. The surgeon must carefully maintain equal tension on both ends of the suture or the knot will slide sideways out of the C-shaped loop. While this type of knot pusher works well with monofilament sutures, it has been found to be ineffective and difficult to use for braided sutures, which are the type often preferred for valve replacement surgery. This is due to the fact that the narrow knot pushing edge within the C-shaped loop places too much pressure against the knot, which tends to make the knot lock up rather than slide along the suture.
Another type of knot pusher has a pair of opposing grooves on the head of the knot pusher with a flat surface between them. Examples of this type of knot pusher can be seen in U.S. Pat. No. 5,234,444 to Christoudias and U.S. Pat. No. 5,217,471 to Burkhart. The flat surface between the grooves allows the device to push directly against the tissue that is being sutured and it separates the two ends of the suture so that the tension to tighten the knot acts parallel to the tissue surface, which more effectively tightens the knot than pulling the sutures perpendicular to the tissue surface. However, these knot pushers have the disadvantages that they must be reloaded onto the suture every time another throw is added to the knot and they are even more prone to dropping knots than the devices previously described.
A number of surgical knot pushers have been designed to overcome the problem of dropping the knot while transporting it to the surgical site. In general, this type of knot pusher has a pair of eyelets on opposite sides of the head of the device. Examples of this type of knot pusher can be seen in U.S. Pat. No. 5,176,691 to Pierce and U.S. Pat. No. 5,192,287 to Fournier. The two eyelets are very effective at avoiding dropping the knot and at keeping the knot properly centered in front of the device. The disadvantage of having two eyelets is that it makes it more difficult to thread the device onto the ends of the sutures. In addition, each time another throw is added to the knot, at least one end of the suture must be unthreaded from the eyelet end then rethreaded after the knot is made. This adds undue time and complexity to the knot tying procedure.
Another detail of construction that is significant in mitral valve replacement surgery is that, when the replacement valve used is a mechanical valve as opposed to a bioprosthesis, the knot pusher must be made so that no metal parts can possibly come in contact with the mechanical replacement valve. This is because mechanical heart valves are made with highly polished surfaces that may also be coated with a hemocompatible coating such as pyrolytic carbon to reduce hemolysis and platelet attachment. Any disturbance in the surface of the valve or the coating could become a locus for increased hemolysis, thrombogenisis or platelet attachment and thrombosis. This could lead to possibly fatal post-surgical complications. Thus, at least the leading edge of the knot pusher should be made of plastic or another material that will not damage the surface of the replacement valve if there is accidental contact between them during installation. Many of the prior art knot pushing devices are impractical for construction out of plastic because of their complex geometries or a need for high strength in the moving parts. Therefore, they would not be suitable for use in valve replacement surgery.